Machine for forming images



F. P. ALLES MACHINE FOR FORMING IMAGES April 14, 19 4 Filed Feb. 5, 19636 Sheets-Sheet 1 FUGO FRANCIS PETER ALLES BY 73M ATTORNEY April 14, 1964F. P. ALLES MACHINE FOR FORMING IMAGES 6 Sheets-Sheet 2 Filed Feb. 5,1963 FUC6O% INVENTOR FRANCIS PETER ALLES BY @wfamwm ATTORNEY April 14,1964 F. P. ALLES 3, 7

MACHINE FOR FORMING IMAGES Filed Feb, 5, 1963 6 Sheets-Sheet 3 INVHVTORFRANCIS PETER ALLES syl y f ATTORNEY F. P. ALLES MACHINE FOR FORMINGIMAGES F I G. 9

April 14, 1964 6 Sheets-Sheet 4 Filed Feb. 5, 1963 Tl Ii INVENTORFRANCIS PETER ALLES ATTORNEY April 14, 1964 F. P. ALLES MACHINE FORFORMING IMAGES Filed Feb. 5, 1963 6 Sheets-Sheet 5 FIG.IO

' INVENTOR FRANCIS PETER ALLES Filed Feb. 5, 1963 Aprill4, 1964 v F. P.ALLES. 3,128,497

MACHINE FOR FORMING IMAGES 6 Sheets-Sheet 6 FIG. [2

INVENIOR FRANCIS PETER ALLES ATTORNEY United States Patent du Pont deNemours and Company, Wilmington, Del.,

a corporation of Delaware Filed Feb. 5, 1963, Ser. No. 257,053 Claims.(Cl. 18-4) This invention relates to an improved machine for obtaining aclear or light-transmitting image in an opaque pressure-clearable film.

'In Bechtold U.S. Patent 2,957,791 methods are described for selectivelyclarifying the opaque, pressureclearable films covered by said patentthat include pressing the films against a copper engraving, and placingthe film in a typewriter, without an inking ribbon, and typing directlyon it. The pressure-clearable films can be placed against type in aproofing press, and the roller passed over the type to produce a clearimage of the type in the film. The resultant clear image-bearingelements can then be used as negatives for photoprinting.

An object of this invention is to provide a durable and effectivemachine for subjecting an opaque, pressureclearable film to imagetransfer contact with a relief image. A related object is to provide animproved machine for obtaining clear images in such a film by contactingthem with relief printing forms, e.g., type matter, and/or halftones.Yet another object is to provide such a machine which results in clear,sharp images which faithfully reproduce the surface of the reliefprinting form. A further object is to provide such a machine which issimple in construction, easy to operate and gives uniform, dependableresults. A still further object is to provide such an apparatus whichcan be manufactured economically.

In my prior application Ser. No. 189,891, filed Apr. 4, 1962 there isdisclosed a pressure clarification machine which comprises a plateadapted to support a relief printing form and an opaque,pressure-clearable film in contact with the relief surface, a framemember mounted above and suspended across the printing form adapted tohold a multiplicity of spring fingers of small coactive area in contactwith the upper surface of the film and press the lowerpressure-clearable surface against the relief surface, and means forallowing relative motion of the plate support and the frame memberbearing the spring fingers to subject the film to a stroking pressurefrom said fingers. Additionally, the machine is provided with means forchanging the position of the spring fingers laterally by a predeterminedamount to insure complete and uniform coverage of the Whole surface ofthe film and underlying type form. Preferably, the machine is providedwith a vacuum frame about the form and adapted to hold thepressure-sensitive film in contact with the surface of the relief. I

The invention will now be described wtih reference to the accompanyingdrawings which constitute a part of this application. In the drawings:

FIG. 1 is an isometric view of one form of machine of my priorapplication with a printing form in place and parts in broken-awayconstruction,

FIG. 2 is a plan view of an alternative form of said machine,

FIG. 3 is a front elevation of the alternative form of said machine,

FIG. 4 is a side elevation of the alternative form of said machine,

RIG. 5 is a plan view of a segment of the spring fingers of saidmachine,

FIG. 6 is an elevation of the spring fingers,

FIG. 7 is an end elevation of the transverse support 3,128,497 PatentedApr. 14, 1964 block with assembled spring fingers and adjusting plate(Sheet 1 of the drawing containing FIG. 1);

FIG. 8 is an end elevation of the transverse support block with analternative adjustment plate (Sheet 1 of the drawing containing FIG. 1);

FIG. 9 is a plan view of the modified machine with the tiltingmechanism;

FIG. 10 is an enlarged plan view of one end of the support block andrelated tilting mechanism;

FIG. 11 (on Sheet 4 with FIG. 9) is an enlarged end elevation of one endof the support block and related tilting mechanism;

'FIG. 12 is an enlarged sectional view of a portion near one end of thesupport block taken along the line 12-12 of FIG. 11 showing the tiltingmechanism;

FIG. 13 is a detail, in elevation with parts in section, of the cam andcam follower lever; and

FIG. 14 is a detail, in elevation with parts in section, of theactuating handle.

Reference is now made to FIG. 1 of the drawing which illustrates onepractical embodiment of the invention. In this figure and in the otherfigures of the drawing, similar reference numerals refer to similarparts throughout the several figures. In FIG. 1 the image formingmachine comprises a bedplate vlil which carries a relief printing form11 on which is laid a pressure-clearable film 1-2. Fastened to thebedplate in any suitable manner are vertical supports 13 which carryguide rails 14 which extend along the sides of the bedplate. These guiderails are provided with suitable stop collars 15 which are fastened toguide rails by means of set screws 16. Slideably mounted on the guiderails is a transverse frame 17 having end plates 18 which are providedwith suitable holes 19 which interfit with the guide rails. Extendingbetween and fastened to the endplates are transverse rails 20 on whichthere are slideably mounted bearing supports 21. The inner surface ofthese bearing supports are provided with vertical grooves '22 which areadapted to receive transverse support block 23. The bottom surface ofthis support block is provided with a row of spring fingers 24 which areattached to the support block by means of a fastening plate 25 which isheld in position by suitable screws 26.

On the sides of the support block or member are transverse springadjusting plates 27. These plates have a plurality of elongated holes28' through 'which extend bolts 2 9 that are threadably engaged in thesides of the support block. This arrangement of parts is shown morefully in FIG. 7 of the drawing although the form illustrated in FIG. 1is that shown in FIG. 8. The bottom inner, edge of the plates areprovided with a groove 30 that is adapted to receive the extended upperend of the spring fingers.

The transverse rails are provided with springs 31 which surround therails and press against the inner face of the bearing supports andsuitable collars 32 that are fastened to the transverse rails by setscrews 33.

Ratchet wheel 34 is disposed near one end of the transverse framebetween endplate 18 and the bearing support 21. This ratchet wheel hasaffixed thereto a suitable shaft (not shown in FIG. 1) the inner end ofwhich is threaded for threadable engagement with the bearing support.

The opposite end of this shaft is smooth and extends through theendplate. A crank wheel 35 is suitably fastened to the outer end of theshaft. The crank wheel in turn is provided with a suitable crank handle36. Between the ratchet wheel and the inner surface of the endplate andpivotally mounted on the shaft is a cam arm 37. Pivotally mounted onthis cam arm is a pawl 38, the end of which engages the ratchet wheel.The other end of this pawl has mountedthereon a spring pintle 39.

A similar pintle 40 is fastened to the cam arm and mounted on thesepintles is spring 41. As shown in FIG. 1, the outer end of the cam armhas a lateral extension 42 on which is fastened a pintle 43 on whichthere is journalled a roller 44. This roller is adapted to engage withthe surfaces of cams 45 which are adjustably mounted on the bedplate inany suitable manner. As shown in FIG. 1, these cams are disposed in alongitudinal channel 46 in the bedplate. The cams can be fastened inthis channel in any suitable manner, for example, by means of threadedbolts (not shown) which extend through the adjusting slots 47.

In operating the machine shown in FIG. 1 of the drawing, the printingform 11 is placed on the bedplate and, if necessary, fastened to it byany suitable means. The pressure-clearable film is then laid over therelief surface of the printing form. The pressure-clearable film can betaped to the printing form or to the bedplate by means of any suitablepressure-sensitive sealing tape. Alternatively, the film to be used canbe held in place by vacuum; for example, a vacuum frame 48 having asuitable sealing gasket 49 can be placed around the printing block. Aprotective sheet 50 can then be placed over the vacuum frame but is notessential with films having an impervious support. Air can then bewithdrawn in the space between the vacuum frame, the printing block andthe film or the protective cover sheet in any suitable manner, e.g., byproviding suitable connecting passages and hoses or conduits connectedto a vacuum pump.

The spring fingers are then adjusted to the desired height, so that thebottom actuating surface presses against the pressure-clearable film orprotective sheet with the desired amount of pressure. This may varysomewhat depending on the nature of the surface of the relief. It maydiffer with halftones and line or type matter.

The transverse frame is then grasped and actuated to and fro on theguide rails. As the transverse frame and associated mechanism isreciprocated, the bottom surfaces of the spring fingers will have astroking action on the pressure-clearable film. The frame can beactuated by hand or can be actuated automatically by means of hydrauliccylinders or reversible motors suitably connected to the frame so thatit can be reciprocated back and forth along the guide rails.

At the end of each stroke, the cam roller will engage the respective camto actuate the ratchet wheel and thereby move the transverse supportblock laterally a short distance.

Alternatively, one of the cams can be removed so that the transversesupport block can be moved a small increment of distance only after acomplete double movement of the transverse frame.

The initial position of the transverse support block can be adjusted byturning the crank by means of the crank handle 36.

As shown in FIG. of the drawing, the spring fingers are narrow,elongated portions of a single sheet and the bottom surface of eachfinger segment has a depressed surface area of even lesser coactive areathan that defined by the width of the individual finger segments. Thesedepressed areas are designated 24.

In FIGS. 2, 3 and 4 of the drawing there is disclosed an alternativemachine. This machine differs from that shown in FIG. 1 in that thebedplate, printing form, pressure-clearable film, and associated partsare adapted to be moved longitudinally with respect to the transversesupport block and spring fingers. Thus, the transverse frame is fixedand the bedplate capable of movement back and forth in a horizontalplane.

In the machine as shown in FIGS. 2, 3 and 4 of the drawing, a horizontalrectangular frame 60 carries on its upper surfade along one side aV-shaped ridge 61 that is adapted to receive a 'slideable bedplate 62.The bottom 4 surface of the bedplate is provided with a suitablecoacting groove member 63 which interfits with and rides on the V-shapedridge. The edge of the bedplate opposite the V-shaped groove members hasmounted thereon suitable pintles 64 on which there are journalledrollers 65. These rollers are adapted to roll along the upper surface ofthe horizontal frame. A rectangular frame member 66 is fastened to theslidable bedplate in any suitable manner. A suitable printing form, notshown in FIGS. 2-4, is adapted to be placed on the surface of theslideable bedplate and within the confines of the rectangular frame.

Vertical support members are mounted'on the horizontal frame near itsouter side edges and preferably near the central part of the sides.These supports 60 can be integral with the frame and can be welded,bonded, or otherwise affixed to the frame member. Extending betweenthese vertical supports are transverse guiderails 68 on which there areslideably mounted end plates 69. The ends of these rails can be threadedand held in place by means of nuts 70. Extending between these endplates and fastened thereto is a transverse crossbrace 71 on which thereis adjustably mounted a transverse support block 72. The ends of thissupport block fit into a vertical groove 73 in the inner surface of eachof the endplates. The transverse support block is fastened to thecross-brace by means of adjusting screws 74 that have threadableengagement with threaded holes in the support block. These adjustingscrews extend through the cross-brace and through suitable threadedcollars 75 between the bottom surface of said cross-brace and the topsurface of the support block. The collars are adjusted by means ofradial holes 76, disposed about the peripheries into which a rod orspanner may be inserted to turn them. The row of spring fingers 77 isfastened to the bottom surface of the support block in the same manneras described above with reference to the machine shown in FIG. 1. On thesides of the support block there are similarly mounted transverse springadjusting plates 78. These plates have elongated holes 79 extendingtherethrough, through which there are inserted bolts 80 that threadablyengage the support block.

Mounted on the transverse rail '68 are collars 81 that are fastened inposition by means of suitable set screws 82. Springs 83 extend aroundthese rails and press against the respective collars and inner surfaceof the endplates.

The transverse cross-brace can be fastened to the endplates in anysuitable manner, e.g., by means of countersunk screws 84 whichthreadably engage holes in the endplates.

A ratchet wheel 85 disposed between one of the endplates and one of thevertical supports, is provided with a suitable shaft the inner end ofwhich has a screw thread for engagementwith coactive screw threads (notshown) in the endplate. The outer end of the shaft 85- has a smoothsurface and extends through a suitable hole 86 in the endplate. Betweenthe ratchet wheel and the. endplate, and journalled on the shaft, is acam arm 87. Pawl 88 is pivotally mounted on this cam arm and has adetent 8 9 that engages with the ratchet wheel. If desired, this pawlcan be provided with a suitable pintle on which there is mounted one endof a spring, the other end of which can be mounted on a similar pintleon the cam arm in a manner similar to that shown in FIG. 1. For the sakeof clarity, the details of this are not given in FIGS.

The cam arm has a lateral section which carries a pintle 90* on whichthere is journalled a cam roller 91. This cam roller is adapted to coactwith suitable cams 92 mounted on the longitudinal side rails 93 that arefastened to the slideable bedplate in any suitable manner.

As shown in FIG. 4, an outer end of these side rails is provided with anupwardly extending arm portion 94. Extending between and fastened tothis arm portion is a transverse handle 95.

If desired, the outer end of the shaft of the ratchet Wheel can beprovided with a crank so that the ratchet wheel can be turned by theoperator at any desired mo ment. A crank and crank handle like thatshown in FIG. 1 can be used.

The machine of FIGS. 2, 3 and 4, in general, operates in essentially thesame way as that of FIG. 1. To be more specific, a printing form isplaced on the slideable bedplate and a sheet of opaquepressure-clearable film is stretched across the top of the printingform. The bedplate is then reciprocated to and fro instead of thetransverse frame of FIG. 1. The spring fingers, ratchet wheel, etc.operate essentially in the same way as in the machine of FIG. 1 and toavoid repetition, the details are not given again. 1

The distance the transverse support block is maintained above thesurface of the printing form can be adjusted by turning screws 74 andcollars '75.

With particular reference to FIG. 1, the rails 14 can, if desired, bemounted in blocks that can be adjusted upwardly and downwardly, thuspermitting further adjustment of the distance of the spring fingers fromthe surface of the printing form. These blocks can be spring loaded. Therails 68 can be mounted similarly for adjustment in vertical supports60.

In FIG. 8 of the drawing, there is shown an alternative form of supportblock. In this form the adjusting plate 25 is wider than the block andcontacts with the slanting bottom surfaces of the spring fingers. Itsdistance from the bottom of the block 23 is adjusted by a suitable shim96 and locked by means of screws 26.

By substituting shims of different thicknesses, one can attain furtheradjustment in the action of the spring fingers.

The improved machine of this invention, as exemplified in FIGS. 9-14 ofthe accompanying drawing and below, differs from the basic machinedescribed above and in my prior application in that the support blockfor the spring fingers is pivotally mounted so that it can be tiltedfrom its normal longitudinal vertical axis whereby one row of the doublerow of spring fingers is raised from op- I erative contact with thedesired surface or plane.

For purposes of explanation, it is to be assumed that spring fingersupport block 23 (or 72) is shortened. An endplate 101 is fastened toeach end of support block 23 by means of screws 102 which extend intosuitable threaded holes (not numbered) in each said end. Each endplatefits into vertical recess 103 in the inside surface of pivot block 104-.Stud 105 extends laterally from the outer surface of the pivot block,preferably from the lower central part of said block. The stud fits intoa pivot hole 106 in the inner surface of bearing supports 21. The upperend of the pivot block is provided with a horizontally disposed hole 107preferably an oval hole, through which there extends locking screw 108that has threaded engagement with the endplate 101. Between head 109 ofthe locking screw and the surface of bearing support 21 is a largewasher 110. Handle 111 attached to head 109 extends laterally from thehead.

As shown best in FIGS. 9 and 10, an actuating bar or shaft 112 extendsacross the entire unit and parallel to transverse cross-brace 71 andsideplates 123. On each end of the actuating bar there is (fastened inany suitable manner (e.g., by keys or setscrews) a cam stop 113. Thepoint of maximum rotation of the cam stop is determined by adjustingscrew 114 which has threadable engagement and extends through sideplates123. Nut 115 locks the screw in the desired position of adjustment.

There are also fastened to the actuating bar 112, inwardly from the camstops, cams 11 6. Suitable fastening means, shown best in FIG. 13 arekeys 117 which interfit with suitable kcyways (not shown) and are heldin place by set screws 11%. Immediately above each cam is a cam followerarm 119 which is fastened by means of screws 120 to transverse frame 117'(or 71). As shown in FIG. 14, attached to integral collar 121(extension of the cam) is a lateral actuating handle 122.

0n the side of transverse frame 17 (or 71) opposite from the supportblock and extending through one of transverse side plates 123 aresuitable adjusting screws 124 which interfit with threaded holes (notnumbered) in the sideplaite. Outer locknut 125 locks the screw in theadjusted position. Also mounted on each screw 124 is a nut 12:6, washer129 and spring 128 which presses against said washer and the side of thesupport block.

In using the modified machine just described, the spring fingers on theleading side of the support block which first contact the printing formwhen the block is moved from left to right (see FIGS. 9 and 11) arepre-stressed approximately 0.05 inch by raising the support block 27(see FIG. 7). Initially, cams 116 are set so that the center line of thesuport block is in a vertical plane. The spring fingers on the followingedge of the block (the right side) are not pre-stressed, i.e., the plate27 on that side of the support block is dropped so that the ends of thefingers barely touch the bottom of slot 30. The spring finger assemblyis then adjusted to the desired position by means of screws 74 andcollars 75 to bring the coactive surface of the trailing spring fingerswithin the range 0.005 to 0.030 inch below the printing surface of theprinting form. This constitutes the tacking position of the springfinger assembly on the initial pass of the assembly across the surfaceof the printing form. Handle 122 is rotated to actuate cams 1116 wherebythe cam follower lever and spring finger assembly is rotated in acounterclockwise direction around the center line of studs 105. Thisrotation and tilting of the support block raises the row of trailingspring fingers from the printing form.

The extent of the rotation of the support block is adjusted by means ofscrew 114 so that the contact surfaces of the leading row of springfingers are approximately 0.015" below the printing surface of theprinting form. The leading row of spring fingers is then set up for theproper clarification pressure. In operation, handle 122 is rotated tobring the contacting surface of the row of trailing spring fingers intothe tacking position. The unit isthen made to traverse back and forthover the printing form. If, for example, the traversing mechanism is setfor 0.002 inch lateral movement per stroke, the units then operate for.about 34 strokes. This initial operation serves to tack-down thepressure-clearable film onto the surface of the type form by wiping airfrom under the film where it contacts the printing surface of theprinting form. This produces a low degree of embossing which preventsanyshifting between thefilm and the type form. After this initialtack-down operation, the handle 122 is rotated in the reverse directionto lower the lead-. ing row of spring fingers into contact position andthe unit is operated for an additional stroking action, elg., about 34or more strokes, at which time adequate clarification of thepressure-sensitive film is attained and clear images corresponding tothe surface of the printing form are obtained.

In each of the different machines described above, especially where thebedplate is stationary and the unit embodying the spring fingers isdesigned to travel back-andforth over the printing form, the fingersupport and rocking mechanism can be replaced by an arrangement ofsimple flex-rod suspensions. To do this, the spring support member 23may be replaced by a tubular element supported at each end by a bearingblock fitting in an enlarged hole in the sliding supports 18. Thepositioning of the tubular bearing support is obtained by flex-rodsmounted at the top and bottom of each tubular bearing block and theother ends of the rods are afiixed to the sliding support 18 to form aparallelogram supporting system permitting vertical movement of thetubular bearing support. The vertical adjustment is obtained by movingthe screw elements 74 and 75 into the sliding supports 18. To maintainlateral stability one end of another flex-rod is attached to slidingsupport 18 and the other end is attached to the tubular finger support.The transition from tack-down position to clarification position isobtained by rotation of the tubular finger in its bearings. The degreeof rotation can be established by means of adjustable stops mounted onthe tubular bearing blocks. The tubular bearing blocks are split, sothat they may be compressed by meansof a suitable screw to lock thetubular finger support in the desired fixed position during operation.

Alternatively, the guide rails -14 could be eliminated and endplates 18allowed to bear on and slide on the bedplate. Suitable beads or channelscan be provided to insure traversing in a straight line.

In place of the motor driving mechanism referred to above, theback-and-forth traversing action can be achieved by means of tworecirculating chain drives, driven by a non-reversing motor, disposedalong each side of the bedplate. Such a drive would provide forward andreverse action from an inexpensive unidirectional main drive, a fixedlength of stroke, a constant speed while the spring fingers are incontact with the surface, and a smooth sinusoidal deceleration andreversal at each end of the stroke.

The various structural parts of the machines described can be made ofconventional materials of construction. For most of the members andparts, steel, steel alloys, brass, aluminum, aluminum alloys, and highstrength plastics, e.g., polyacetal resins, glass fibre laminates,nylon, etc. may be employed. For the spring fingers, it is preferred touse hardened beryllium copper, but Phosphor bronze, spring steel, etc.may be employed. The wearing surface of the fingers may be plated orcoated with hard, abrasion-resistant material, e.g., chromium, rhodium,-tungsten carbide, Stellite, etc. The base plate, bearing blocks, cornersupporting members and transverse blocks, etc, can be made of cast ironor die cast aluminum.

Various types of opaque pressure-clearable films can be used in theapparatus of this invention. As previously stated, suitablepressure-clearable films are described in Bechtold U.S. Patent2,957,791. Other useful supported and unsupported pressure-clearablefilms are described in US. Patents 2,846,727, 2,848,752, and inassignces U.S. application *Ser. No. 63,953, Oct. 21, 1960.

The opaque pressure-clearable films described in Bechtold US. Patent2,957,791 and in the Bechtold patents referred to therein, have alsobeen called opaque pressure-clarifiable or pressure-coalescible films,but are more aptly termed opaque pressure-clearable films since theopaque areas which are highly opaque are converted by means of pressureinto clear areas readily transparent to visible light. The films arealso clearable by heat and by heat and pressure. 1

The pressure-clearable films or coatings of the Bechtold patents whichconstitute preferred materials for use in this invention are porous,opaque, non-fibrous, of low bulk density and are composed of partiallycoalesced discrete particles of a hydrophobic organic addition polymerhaving a wholly carbon chain, a molecular weight of at least 10,000 andbeing taken from the group consisting of vinyl and vinylidene additionpolymers, said film having an open-cell structure characterized bymicroscopic voids communicating with the surface and containing 20% to80% by volume of open-cell pores, said film having a permeability towater vapor of at least. times greater than that of correspondingnon-porous films .of the same polymer and thickness, the opacity perunit of thickness being such that a film thickness of 3 mills andgreater has a light-transmission of less than 10% at 4000 A., andincreased light transmission at longer wavelengths of light, said filmbeing capable of sustaining a permanent reduction in thickness of atleast 20% together with substantial clarification of opaqueness under apressure of 10,000 pounds per square inch at room temperature. Thesefilms are more fully described and defined in Bechtold US. Patent2,957,791 which constitutes part of this disclosure.

After the clarified, or clear, opaque pressure clearable films by usingthe machines of this invention, the opaque background areas can beincreased in optical density by deposition of opaque material in suchareas to provide a high-contrast image-bean.

ing layer. These areas being porous are readily coated or impregnatedwith colorants which fill the open cell voids. Any of thepostdensification procedures described in assignees Bechtold U.S.application Ser. No. 63,953 can be used. Thus, the selectively clarifiedcoating can be post-der1sified in unchanged opaque background areas byin situ deposition of lead sulfide at 50 C. by immersing the coating inaqueous lead nitrate and sodium sulfide solutions with intermediateblotting with porous cardboard, washing in water and drying which givesa dense, black background. Alternatively, the background areas can bepost-densified by dyeing for several minutes with 2.5% aqueous solutionof an after-chromed dye, Colour Index No. 15,710, at 50 C. for severalminutes.

While, for simplicity, the machines described are shown with a doublerow of off-set spring fingers, it is obvious that a single row ormultiple rows of larger number might be employed. In addition, while themachines have been shown as operating in essentially a straight linefashion, the machine can be modified so that the finger assembly canbe'rotated over the relief plate surface in a horizontal plane or fixedabove the relief plate surface and the bedplate rotated beneath thefingers. In a machine with straight line motion of the type shown, it ispreferable to have the horizontal relief surface at a slight angle, forinstance, up to about 10 to a main axis of the plate or line of travelof the machine. This prevents all of the fingers from dropping below thetype surface at the same time and makes for smoother operation.

While the contacting area 24' of the spring fingers, i.e., the sphericalsurface on the spring fingers, may vary in size, surfaces having radiiof about .008 to .016 inch are desirable sizes, because these sizes willclarify a .00 to .003 inch width of line and the smaller characters onmost relief printing forms are approximately .003 inch in their smallestdimension. The loading on the spring fingers depends upon thecharacteristics of the opaque, pressure-clearable film. The loadrequired to clarify a typical such film having a pressure clarifiablelayer of about .0005 inch on a .002 inch polyethylene terephthalate baseusing a .019 inch radius spherical clarification element, isapproximately grams weight, which will produce substantially minimumoptical density. The spring fingers are prestressed to obtain pressuresufficient for clarification; and as shown in the drawings, the depth ofpenetration below average type height is controlled. On a typical reliefprinting form, average type height is 0.918 inchi003 inch; and,conveniently, the penetration of the fingers should be from .010 inchto- .005 inch below average type height for satisfactory operation.

A convenient spacing of lines obtained with the double row of fingersshown is about .033 inch. Obviously the closer the lines, the fewer thenumber of passes required to obtain adequate coverage of the entiresurface. However, there are limitations on the dimensions of the fingersand slots. The length, width and thickness of the fingers are dictatedby the materials used in constructing them, the pressure required forclarification, and the need to prevent excessive lateral movement whenthe finger passes over a line oriented at an angle to the path or whenthe type face is curved. The fingers can be separate and inserted in ablock. They can be' made of resins or superpolymers and have inserts ofmetal at the area of contact.

To obtain maximum clarification with the machines and fingers described,the fingers should be moved about .001 inch laterally for eachsuccessive pass.

The apparatus of this invention has the advantage images are formed inthe that it is simple in construction but dependable in operation. Whenused as described above, it will faithfully reproduce a printing reliefforming a clear and transparent image of the relief in the ouaquepressure-clearable film element. The apparatus has the advantage that itis readily adaptable for obtaining photographic negatives ortrnsparencies from a wide variety of printing reliefs including typeforms, engraved plates, photopolymerized printing reliefs, halftones,combined halftones and line printing forms, etc.

Another advantage is that the various parts of the apparatus are simplein construction, easy to assemble, require little attention to keep themin operative condition, and have good wearing properties. A furtheradvantage is that the machine does not require much space and isrelatively inexpensive.

A still further advantage of the ordered method of clarificationemployed by these machines is that the pressure applied to any onecharacter can be reduced to a minimum and the depth of penetration inshallow relief areas can be controlled. In addition, uniform coverage ofthe surface to be reproduced is insured.

A particular advantage of the invention is that it permits one torapidly convert a printing relief into a photo graphic transparency,accurately reproducing as a clear image all of the fine detail of therelief. The apparatus has an addition advantage that it does not damagethe surface of the relief or type form and gives an adequate, clearimage in an opaque pressure-clearable film in a short time. It avoidsthe use of heavy pressure rollers such as those used in pulling a prooffrom a bed of type which often damages the type surface and cannot besuccessfully used where fine rulings are in the printing surface. Animportant advantage of the improvement of this invention is that thepressure-senstive film can be tacked-down by the tilting mechanism ontothe surface of the film and it will not shift when the leading andfollowing rows of spring fingers are used to complete clarification.This is particularly advantageaus when forming a clear image in apressure-clearable film in contact with a halftone printing form orplate.

Still further advantages will be apparent from the foregoing descriptionand accompanying drawings.

I claim:

1. An improved image-forming machine having:

(A) a horizontal bedplate adapted to support a relief printing form andan opaque pressure-clearable film in contact with the relief surface ofsaid form,

(B) a frame member having a transverse support member extending acrosssaid bedplate,

(C) a row of spring fingers of small coactive area adjustably mounted onthe bottom surface of said member, the coactive area of the fingersbeing adapted to contact with the upper surface of such a film and pressthe lower surface of the film against the relief surface of said form,and

(D) means for allowing relative motion between the bedplate and framemember to subject the film to a stroking pressure from said fingersduring the motion;

characterized in that the transverse support member is pivotally mountedso that said member can be tilted about a transverse axis to vary theposition of contacting surfaces of the row of fingers above thebedplate.

2. An improved image-forming machine having:

(A) a horizontal bedplate adapted to support a relief printing form andan opaque pressure-clearable film in contact with the relief surface ofsaid form,

'(B) a frame member having a transverse support member extending acrosssaid bedplate,

(C) a spaced double row of spring fingers of small coactive areaadjustably mounted on the bottom surface of said member, the coactivearea of the fingers being adapted to contact the upper surface of such afilm and press the lower surface of the film against the relief surfaceof said form, and

(D) means for allowing relative transverse motion in a horizontal planebetween said bedplate and support member to subject the film to astroking pressure from said fingers during said motion;

characterized in that the transverse support member is pivotally mountedon the frame member whereby said support member can be tilted about atransverse axis and raise one row of spring fingers from film contactposition.

3. An improved image-forming machine having:

(A) a horizontal bedplate adapted to support a relief printing form andan opaque pressure-clearable film in contact with the relief surface,

(B) a frame member extending across said bedplate and having mountedthereon for adjustment in vertical and horizontal directions -.atransverse support member,

(C) a spaced double row of spring fingers of small coactive area adjustably mounted on the bottom surface of said support member, thecoactive area of the fingers being adapted to contact with the uppersurface of such a film and press the lower surface of the film againstthe relief surface of said form, and

(D) means for allowing relative transverse motion in a horizontal planebetween said bedplate and support member to subject the film to astroking pressure from said fingers during said motion;

characterized in that the transverse support member is pivotally mountedon the frame member whereby said support member can be tilted about atransverse axis and raise one row of spring fingers from film contactposition.

4. An improved image-forming machine having:

(a) a fixed horizontal bedplate adapted to receive a relief printingform and an opaque pressure-clearable film in contact with the reliefsurface thereof,

(b) vertical supports fixedly mounted on said bedplate having guiderails extending between the supports along each side of the bedplate,

(c) a transverse frame member slideably mounted on said guide railshaving a laterally and vertically adjustable support member mountedthereon,

(d) a double row of spring fingers of small coactive area mounted on thebottom surface of said support member, the coactive area of the fingersbeing adapted to contact with the upper surface of such a film and pressthe lower surface of the film against the relief surface of said form,

(2) a ratchet wheel, spring-biased pawl and a cam arm carried by saidframe member,

(1) means carried by said frame member for turning said ratchet wheeland laterally adjusting said member, and

(g) cams mounted on said bedplate to cooperate with said cam arm andseparately turn said ratchet wheel and adjust the lateral position ofsaid member,

characterized in that the transverse support member is pivotally mountedon the frame member whereby said support member can be tilted about atransverse axis and raise one row of spring fingers from film contactposition.

5. An improved image-forming machine having:

(1) a fixed horizontal frame,

(2) a bedplate slidably mounted on said frame and adapted to receive arelief printing form and an opaque pressure-cleariable film in contactwith the relief surface of said form,

(3) vertical supports fixedly mounted on said frame,

(4) transverse guide rails extending between said supports and acrosssaid printing form,

('5) a laterally and vertically adjustable member slideably mounted onsaid transverse rails,

(6) a double row of spring fingers of small coactive area mounted on thebottom surface of said support member, the coactive area of the fingersbeing 11 adapted to contact with the upper surface of such a film andpress the lower surface of the film against the relief surface of saidform,

(7) a ratchet wheel carried by said vertioa-l supports and having ascrew thread engagement with said member,

(8) a spring-biased pawl and a pawl arm carried by said verticalsupports,

(9) a cam roller carried by said arm and a cam carried by said slideablebedplate for actuating cam roller and pawl arm, to turn said ratchet'wheel, and

(10) means for separately turning said wheel to adjust said supportmember laterally;

References Cited in the file of this patent UNITED STATES PATENTS1,516,772 La Bareteaux Nov. 25, 1924 2,366,827 Ayres J an. 9, 19452,827,942 Shultz Mar. 25, 1958 2,928,708 Ellison et a1. Mar. 15, 1960

1. AN IMPROVED IMAGE-FORMING MACHINE HAVING: (A) A HORIZONTAL BEDPLATEADAPTED TO SUPPORT A RELIEF PRINTING FORM AND AN OPAQUEPRESSURE-CLEARABLE FILM IN CONTACT WITH THE RELIEF SURFACE OF SAID FORM,(B) A FRAME MEMBER HAVING A TRANSVERSE SUPPORT MEMBER EXTENDING ACROSSSAID BEDPLATE, (C) A ROW OF SPRING FINGERS OF SMALL COACTIVE AREAADJUSTABLY MOUNTED ON THE BOTTOM SURFACE OF SAID MEMBER, THE COACTIVEAREA OF THE FINGERS BEING ADAPTED TO CONTACT WITH THE UPPER SURFACE OFSUCH A FILM AND PRESS THE LOWER SURFACE OF THE FILM AGAINST THE RELIEFSURFACE OF SAID FORM, AND (D) MEANS FOR ALLOWING RELATIVE MOTION BETWEENTHE BEDPLATE AND FRAME MEMBER TO SUBJECT THE FILM TO A STROKING PRESSUREFROM SAID FINGERS DURING THE MOTION; CHARACTERIZED IN THAT THETRANSVERSE SUPPORT MEMBER IS PIVOTALLY MOUNTED SO THAT SAID MEMBER CANBE TILTED ABOUT A TRANSVERSE AXIS TO VARY THE POSITION OF CONTACTINGSURFACES OF THE ROW OF FINGERS ABOVE THE BEDPLATE.